Fixation of APM in chewing gum

ABSTRACT

This invention relates to a product and process in which L-aspartyl-L-phenylalanine methyl ester is fixed in the reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized starch acid-ester of a substituted dicarboxylic acid whereby the decomposition rate of the L-aspartyl-L-phenylalanine methyl ester when employed in a chewing gum system is greatly reduced.

BACKGROUND OF THE INVENTION

Chewing gums are generally comprised of a substantially water insoluble, chewable gum base such as chicle, is substitutes mixtures thereof and the like. Incorporated within this gum base may be plasticizers or softeners to improve the consistency and texture of the gum flavors and sweetening agents such as sugar or corn syrup, or for sugarless gums artificial sweeteners.

L-aspartyl-L-phenylalanine methyl ester (APM) is a dipeptide sweetening agent described in U.S. Pat. No. 3,492,131 and is a desirable chewing gum sweetening agent. Another attribute of APM is that it may be added in effective amounts to a normally sweetened sugar or sugarless chewing gum to produce longer lasting sweetness and flavor as disclosed in U.S. Pat. Nos. 3,943,258 and 3,982,023, which are herein incorporated by reference.

In the normal course of manufacture, shipment and storage of chewing gums, the product is often exposed to relatively high temperatures; i.e., 70° F. to 100° F. plus, for extended periods of time. The stability of APM is temperature sensitive. High temperatures induce the ester linkage to hydrolyze to the dipeptide aspartylphenylalanine. This dipeptide can then cyclize to the corresponding diketopiperazine. When this transition takes place, the sweetness of the APM is proportionately lessened. Thus, the effectiveness of APM in a chewing gum composition is greatly reduced when the gum is subjected to high thermal storage conditions. Therefore, it would be highly desirable if a simple system were devised whereby the decomposition of APM in chewing gum when stored at elevated temperatures could be greatly reduced.

SUMMARY OF THE INVENTION

This invention relates to a sweetened chewing gum composition which comprises gum base, flavor, a bulking agent and L-aspartyl-L-phenylalanine methyl ester (APM) wherein the APM is fixed in an encapsulating agent selected from the group consisting of gum Arabic and a dextrin which is the reaction product of a compound containing a polyvalent metallic ion, with specified ungelatinized starch acid-esters of substituted dicarboxylic acids. APM is useful in chewing gum as a sweetener and as a sweetness and flavor extender.

It is the object of this invention to substantially increase the storage stability of APM when it is combined in the chewing gum confection. Heretofore chewing gum containing APM has been found to lose in excess of 70% of its sweetening potency when stored at 100° F./30% rh for 20 weeks. The product of the instant invention contains APM which is fixed in gum Arabic and/or dextrin. This fixation or encapsulation greatly reduces the amount of decomposition of APM in the gum system.

DETAILED DESCRIPTION OF THE INVENTION

L-aspartyl-L-phenylalanine methyl ester (APM) is a relatively recent development in food technology. It is commercially available from G. D. Searle & Company, Skokie, Ill., under the trademark name EQUA 200. It is a sugar substitute with a sweetening potency approximately 200 times that of sucrose.

    ______________________________________                                         TYPICAL ANALYSIS FOR FOOD GRADE EQUA 200                                       ______________________________________                                         Identity                                                                       A.  Appearance:        White Crystalline powder                                B.  Odor:              Almost odorless (very                                                          slight acetic odor)                                     C.  Taste (0.07% in water):                                                                           Clean, sweet taste, free of                                                    significant bitter, sour,                                                      or salty off-notes                                      D.  Chemical identity tests                                                        1. Amino Acid:     Positive                                                    2. Ester           Positive                                                E.  Specific rotation in                                                           15N formic acid:   +15.91                                                  F.  pH of the 0.8% solution:                                                                          5.32                                                    Assay                                                                          Titration by Lithium Methoxide:                                                                   99.9%                                                       Purity                                                                         A.  Clarity and color of                                                           solution (0.8%     Clear and colorless, no                                     solution):         suspended particles                                     B.  Transmission of                                                                solution (1% in 2N HCI):                                                                          99% at 430 nm                                           C.  Loss on drying (105°                                                    C/4 hours):        3.9%                                                    D.  Residue on ignition:                                                                              0.04                                                    E.  Heavy metal:       5 ppm                                                   F.  Arsenic:           0.1 ppm                                                 G.  Diketopiperazine:  0.5%                                                    Microbiological                                                                A.  E. coli            Negative                                                B.  Salmonella         Negative                                                C.  Coagulase + Staph  Negative                                                ______________________________________                                    

L-aspartyl-L-phenylalanine methyl ester is a highly desirable replacement for sugar or sucrose in such comestibles as breakfast cereals, dry bases for beverages, gelatin foods, filling and diary product analogue toppings. However, APM contains an ester linkage that under certain moisture, temperature and pH conditions a hydrolyze to the dipeptide aspartylphenylalanine. The dipeptide can then cyclize to the corresponding diketopiperazine (DKP).

A potential for APM to go spontaneously to DKP results in a proportional loss of product sweetness. Thus products which are subjected to extreme heat such as baking are incompatible with APM. Further, the products which do incorporate APM will have substantially diminished sweetening potency when adverse conditions such as elevated storage temperatures are encountered.

A chewing gum system is particularly enhanced by incorporating APM within it. As a basic sugar substitute, as disclosed in U.S. Pat. No. 3,642,491a sugarless chewing gum may be obtained which has a clean sugar-like sweetness and in which no synthetic flavor or after-taste is perceived. U.S. Pat. No. 3,943,258 teaches that the addition of APM to sugar and sugarless chewing gum compositions in effective amounts extends a time period over which both flavor and sweetness are discernible during chewing. According to the practice of the instant invention, the APM may be used as the sole sweetener in a chewing gum composition or added to a sweetened chewing gum as an enhancer or extender.

The gum base may be any chewable, substantially water insoluble base such as chicle and substitutes thereof, guttagkay, sorva, jelutong, synthetic polymers such as polyvinyl acetate, synthetic resins, rubbers, and the like and mixtures of these materials. The amount of gum base employed may vary widely depending on the type base used and other ingredients making up the final gum product and other like factors. Generally, however, it has been found that anywhere from 15 to 40% by weight of the final gum composition may be used and preferably from about 20 to about 30%. Plasticizers or softeners such as lanolin, propylene glycol, glycerol and the like and mixtures thereof may optionally be incorporated within the gum base to achieve a desired texture and consistency. Generally, the flavors employed in chewing gums may be the essential oils or synthetic flavors or mixtures of these. Flavors such as wintergreen, spearmint, peppermint, birch, anise, fruit flavors, and the like may be used satisfactorily with the variety of gum bases. The amount of flavoring material is normally a matter of preference, but may be subject to the consideration of such factors as type of flavor used and the type of base used and the like. Generally, flavoring materials account for about 1% by weight of the total gum composition.

In order to obtain a sweetened gum, the remaining portion of the gum composition is generally a sweetener such as sugar or for sugarless gums a sugar substitute. By sugar we mean sucrose, dextrose, corn syrup solids (their substitutes) and the like and mixtures thereof. Sugar substitutes may be any sweetening agent used in sugarless gum such as mannitol, sorbitol, xylitol, saccharin, cyclamate, dihydrochalcone and dipeptides, particularly L-aspartyl-L-phenylalanine methyl ester. Sugar and sugar alcohols may also be defined as bulking agents and generally comprise a major amount by weight of the total gum composition. Additionally, non-sweet bulking agents such as hydrolyzed cereal solids may be included in the gum composition.

The basic concept of the instant invention resides in fixing or encapsulating the APM in order to retard and/or prevent the conversion of APM to DKP under certain moisture, temperature and pH conditions which affect a chewing gum system. It has been found that APM may be successfully fixed in gum Arabic and a particular dextrin which is commercially available under the registered trademark name Capsul® as manufactured by National Starch and Chemical Corporation, New York, N.Y.

Physical Properties

Color--White to off-white

Form--Powder

pH--3 (approx.)

Moisture--5% (approx.)

Capsul® dextrin, as disclosed in U.S. Pat. No. 3,091,567, is a reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized starch acid-ester of a substituted dicarboxylic acid. Such starch acid-esters may be represented diagrammatically by the following formula: ##STR1## where R is a radical selected from the class consisting of dimethylene and trimethylene radicals, and R₁ is a hydrocarbon constituent selected from the class consisting of alkyl, alkenyl, aralkyl or aralkenyl groups. The above-described ungelatinized starch acid-esters are prepared by reacting an ungelatinized starch, in an alkaline medium, with a substituted cyclic dicarboxylic acid anhydride having the following formula: ##STR2## where R and R₁ represent the same substituent groups as are listed above for those same symbols. Substituted cyclic dicarboxylic anhydrides falling within this formula are the substituted succinic and glutaric acid anhydrides.

In the preferred embodiment of this invention, the APM fixation is accomplished by spray drying prior to incorporating it into the chewing gum. Other methods such as coacervation may be employed. The spray drying process comprises forming an emulsion of APM and the gum Arabic or dextrin in a continuous aqueous solution. The emulsion is then passed through a spray nozzle and broken up into numerous droplets. The droplets are introduced into a drying environment and as their moisture is given up the droplets are formed into solid particles. The APM now exists as part of the solid matrix which is to be incorporated in a chewing gum formulation.

In the preferred embodiment of the instant invention, an aqueous solution of APM and an encapsulating agent are passed through a positive displacement homogenizer at pressures between 250 psi and 5000 psi and preferably 1500 psi to 2500 psi so that the components are thoroughly mixed and/or emulsified. Next, it is most preferable to introduce the product stream into the body of the spray dryer via a rotating disc-type nozzle. The product stream contacts the disc which may be rotated by separate means or by the pressure of the product stream and thereby the product stream is dispersed into numerous droplets within the spray dryer. The rotating disc allows a more uniform product distribution of the material to be spray dried within the tower.

The temperatures employed in the drying process are typically in an air temperature range of 350° F. to 550° F. on the inlet side and 175° F. to 300° F. on the outlet side. Preferably the inlet temperature is between 375° F. and 425° F. and the outlet temperature is between 200° F. and 250° F. The temperature of the solution entering the dryer is preferably between 60° F. and 120° F. and most preferably between 70° F. and 90° F. The dispersion wheel or rotating disc may operate between about 200 rpm and 1000 rpm and preferably between 550 rpm and 850 rpm. The concentration of solids entering the dryer may be between 10 to 45% solids by weight. Preferably the total solids concentration will be between 20 and 30% by weight.

The ratio of encapsulating agent to APM may vary between about 10:1 to about 2:1 and most preferably will be between 5:1 to 3:1. The ratio of encapsulating agent to APM of the final product will be the same as the ratios comprising the inlet stream since substantially all of the water is removed during drying.

EXAMPLE I

    ______________________________________                                         Peppermint Flavor Chewing Gum                                                  Sucrose/Dextrose Formulation - %                                               ______________________________________                                                                             APM                                                        Control-  APM in    in                                         Ingredient      Free APM  Gum Arabic                                                                               Capsul                                     ______________________________________                                         Chewing Gum Base                                                                               24.000    24.000    24.000                                     Sugar, 6 x      29.197    28.097    28.097                                     Dextrose Monohydrate                                                                           29.000    27.500    27.500                                     Corn Syrup, 45.5°                                                       Baume           15.000    15.000    15.000                                     Glycerol        0.800     0.800     0.800                                      Lecithin        0.200     0.200     0.200                                      APM             0.650                                                          Peppermint Oil                                                                 + Enhancer      1.153     1.153     1.153                                      20% APM Fixed in Gum                                                           Arabic                    3.250                                                20% APM Fixed in Capsul.sup.®                                              Dextrin                             3.250                                                      100.000   100.000   100.000                                    Co-Drying of APM                                                               ______________________________________                                         Dryer diameter:                                                                              12 feet                                                          Total height: 30 feet                                                          Vertical drying height:                                                                      14 feet (which is the distance                                                 between the nozzle and the top of                                              the cone-shaped lower section of                                               the spray dryer.)                                                ______________________________________                                    

Gum Arabic

A solution comprising 240 pounds of gum Arabic, 60 pounds of APM and 110 gallons of water is prepared. The solution is passed through a Mantin-Gaulin positive displacement homogenizer at an operating pressure of 2000 psi. The product stream is fed to the spray dryer via a rotating disc nozzle. The disc is rotated at 800 rpm. The average inlet temperature is 410° F. and the outlet temperature is 215° F. Feed temperature of the solution is 78° F.

Capsul®

The Capsul® is co-dried under the same conditions as the Gum Arabic.

    ______________________________________                                         Preparation of Sugar APM Chewing Gum                                           ______________________________________                                         2000 Gram Batch in 1 Gallon Sigma Mixer                                        1.   Soften gum base in a steam-jacketed sigma-blade mixer                          at 120-130° F. for five minutes.                                   2.   Add the glycerine and lecithin and mix five minutes.                      3.   Add corn syrup, mix five minutes.                                         4.   Add 1/2 the sucrose/dextrose mixture, mix thoroughly.                     5.   Add remaining sucrose/dextrose blended with APM or                             fixed APM, mix thoroughly.                                                6.   Add flavor, mix for two minutes.                                          7.   Pass the gum through sheeting rolls at approximately                           100° F., to a thickness of 0.068 - 0.075".                         8.   Temper the sheets at 70° F./45% RH for 24 hours, score                  into sticks and package.                                                  ______________________________________                                    

    ______________________________________                                          Effect of Fixation on APM Stability                                           Sucrose/Dextrose Peppermint formulations                                                        % APM Loss at 100° F.                                  Sample #                                                                               Description    4wks   9wks 17wks 20wks                                 ______________________________________                                         1       Control-Free APM                                                                              23     38   --    73                                    2       APM fixed in Gum                                                               Arabic         5      12   --    40                                    3       APM fixed in Capsul®                                                       Dextrin        0      16   --    50                                    ______________________________________                                    

EXAMPLE II

    ______________________________________                                         Peppermint Flavor Chewing Gum                                                  Sugarless Formulations - %                                                                                         APM in                                                    Control   APM in     Capsul                                     Ingredient     Free APM  Gum Arabic Dextrin                                    ______________________________________                                         Chewing Gum Base                                                                              27.000    27.000     27.000                                     Sorbitol       47.174    44.574     44.574                                     Sorbo Solution (70%)                                                                          17.300    17.300     17.300                                     Mannitol       6.100     6.100      6.100                                      Glycerol       0.500     0.500      0.500                                      Peppermint Oil                                                                 + Enhancer     1.276     1.276      1.276                                      APM            0.650                                                           20% APM in Gum Arabic                                                                         --        3.250      --                                         20% APM in Capsul®                                                         Dextrin                             3.250                                                     100.000   100.000    100.000                                    ______________________________________                                    

Co-drying of Gum Arabic and Capsul® same as Example I.

    ______________________________________                                         Sugarless APM Chewing Gum Process                                              Procedure for 1,750 Gram Batch                                                 In 1 Gallon Sigma Mixer                                                        ______________________________________                                         1.  Preheat mixer to 150° F. with mixture of steam and water.               It may be necessary to soften base in mixer, or before - adding to             mixer, to get proper mixing.                                               2.  Add base and glycerol, mix 5 - 10 minutes.                                 3.  Add 1/2 of sorbitol and mannitol, blend for 5 - 10 minutes.                4.  Add sorbo solution and mix until uniform (approx. 5                            minutes).                                                                  5.  Preblend APM or fixed APM and remaining sorbitol and - mannitol, and           add to mixer. Shut off steam, allow cold - water to circulate in               jacket. Mix 5 minutes.                                                     6.  Check mix for grainyness. If grainy, mix for additional                        5 - 10 minutes.                                                            7.  Add flavor, mix 2 - 3 minutes.                                             8.  Remove from mixer, pass the gum through sheeting rolls at                      approximately 100° F. to a thickness of 0.68 - 0.075.               9.  Temper the sheets at 70° F./45% RH for 24 hours, score                  into sticks and package.                                                   ______________________________________                                    

    ______________________________________                                         Effect of Fixation on APM Stability                                            Sugarless Peppermint Formulations                                                                   % APM                                                                          Loss at 100° F.                                    Sample #                                                                               Description        4wks   9wks 20wks                                   ______________________________________                                         4       Control-Free APM   22     33   64                                      5       APM Fixed in Gum Arabic                                                                           17     22   43                                      6       APM Fixed in Capsul®                                                       dextrin            21     32   54                                      ______________________________________                                     

What is claimed is:
 1. A chewing gum composition which comprises gum base, flavor, a bulking agent and L-aspartyl-L-phenylalanine methyl ester wherein the L-aspartyl-L-phenylalanine methyl ester is fixed in an encapsulating agent and the ratio of encapsulating agent to L-aspartyl-L-phenylalanine methyl ester is between 10:1 to about 2:1 and the encapsulating agent consists of the reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized starch acid-ester of a substituted dicarboxylic acid, such starch acid-esters represented diagrammatically by the following formula: ##STR3## where R is a radical selected from the class consisting of dimethylene and trimethylene radicals, and R₁ is a hydrocarbon constituent selected from the class consisting of alkyl, alkenyl, aralkyl or aralkenyl groups, the above-described ungelatinized starch acid-esters are prepared by reacting an ungelatinized starch, in an alkaline medium, with a substituted cyclic dicarboxylic acid anhydride having the following formula: ##STR4## where R and R₁ represent the same substituent groups as are listed above for those same symbols, substituted cyclic dicarboxylic anhydrides falling within this formula are the substituted succinic and glutaric acid anhydrides whereby the conversion of L-aspartyl-L-phenylalanine methyl ester to diketopiperazine is greatly reduced.
 2. The composition of claim 1 wherein the bulking agent is sugar.
 3. The composition of claim 2 wherein the bulking agent comprises a sugar alcohol selected from the group consisting of sorbitol, mannitol, xylitol and mixtures thereof.
 4. The composition of claim 3 wherein the L-aspartyl-L-phenylalanine methyl ester is fixed by co-drying an aqueous solution of L-aspartyl-L-phenylalanine methyl ester with an aqueous solution of the encapsulating agent consisting of the reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized starch acid-ester of a substituted dicarboxylic acid, such starch acid-esters represented diagrammatically by the following formula: ##STR5## where R is a radical selected from the class consisting of dimethylene and trimethylene radicals, and R₁ is a hydrocarbon constituent selected from the class consisting of alkyl, alkenyl, aralkyl or aralkenyl groups, the above-described ungelatinized starch acid-esters are prepared by reacting an ungelatinized starch, in an alkaline medium, with a substituted cyclic dicarboxylic acid anhydride having the following formula: ##STR6## where R and R₁ represent the same substituent groups as are listed above for those same symbols, substituted cyclic dicarboxylic anhydrides falling within this formula are the substituted succinic and glutaric acid anhydrides.
 5. The composition of claim 4 wherein the drying method employed is spray drying.
 6. The composition of claim 5 wherein the aqueous solution enters the spray dryer via a rotating disc nozzle.
 7. The composition of claim 6 wherein the ratio of L-aspartyl-L-phenylalanine methyl ester to the co-dried ingredients is between about 5:1 to about 3:1. 